Display tubes are used, inter alia, in television receivers.
Such a display tube is known from U.S. Pat. No. 4,182,974.
Within the scope of the invention, the term "getter" structure is to be understood to mean a part of the display tube which comprises at least a getter holder with getter material. The getter structure is heated during the manufacture of a display tube. In this process getter material is vaporized. The vaporization causes the pressure in the display tube to decrease. Sometimes, however, a display tube exhibits a defect which can be remedied by repairing the display tube. The display tube under repair is opened, i.e. the neck is opened and the vacuum in the display tube is interrupted. After the display tube has been repaired, the neck is closed and the display tube is evacuated. Subsequently, getter material is again vaporized. It is advantageous to replace the getter structure when the display tube is under repair. In the known display tube, the getter structure is secured to a projection on an anode contact located in the cone. The getter structure is secured in a manner such that it can be replaced. To replace the getter structure, the shield is provided with a groove which gives access to the anode contact.
Within the scope of the invention it has been recognized that the groove adversely affects the magnetic shielding and mechanical rigidity of the shield. A reduction of the magnetic shielding leads to picture errors. A reduction of the mechanical rigidity may lead to problems relating to microphonics.